Querying Solr

For the examples in this chapter, I’ll be assuming that you’ve loaded your server up with the books data supplied with the example Solr setup.

The data itself you can see at $SOLR_SOURCE_DIR/example/exampledocs/books.csv. To load it into a server running with the example schema:

cd example/exampledocs
curl http://localhost:8983/solr/update/csv \
  --data-binary @books.csv \
  -H 'Content-type:text/plain; charset=utf-8'

If you’re working through this manual tutorial-stylye, you might want to keep a copy of the books.csv file open in an editor to check the expected results of some of the queries we’ll try.

Throughout the examples, I’ll assume you’ve set up a SolrInterface object pointing at your server, called si.

si = SolrInterface(SOLR_SERVER_URL)

Searching your solr instance

Sunburnt uses a chaining API, and will hopefully look quite familiar to anyone who has used the Django ORM.

The books.csv data uses a schema which looks like this:

Field Field Type
id string
cat string
name text
price float
author_t string
series_t text
sequence_i integer
genre_s string

and the default search field is a generated field, called “text” which is generated from cat and name.


Dynamic fields.

The last four fields are named with a suffix. This is because they are dynamic fields - see Reading a Solr Schema.

A simple search for one word, in the default search field.

si.query("game") # to search for any books with "game" in the title.

Maybe you want to search in the (non-default) field author_t for authors called Martin


Maybe you want to search for books with “game” in their title, by an author called “Martin”.

si.query(name="game", author_t="Martin")

Perhaps your initial, default, search is more complex, and has more than one word in it:



Sunburnt query strings are not solr query strings

When you do a simple query like query("game"), this is just a query on the default field. It is not a solr query string. This means that the following query might not do what you expect:

si.query("game thrones")

If you’re familiar with solr, you might expect that to return any documents which contain both “game” and “thrones”, somewhere in the default field. Actually, it doesn’t. This searches for documents containing exactly the string “game thrones”; the two words next to each other, separated only by whitespace.

If you want to search for documents containing both strings but you don’t care in what order or how close together, then you follow the example above and do si.query("game").query("thrones"). If you want to search for documents that contain game OR thrones, then see Optional terms and combining queries.

Since queries are chainable, the name/author query above could also be written


You can keep on adding more and more queries in this way; the effect is to AND all the queries. The results which come back will fulfil all of the criteria which are selected. Often it will be simplest to put all the queries into the same query() call, but in a more complex environment, it can be useful to partially construct a query in one part of your program, then modify it later on in a separate part.

Executing queries and interpreting the response

Sunburnt is lazy in constructing queries. The examples in the previous section don’t actually perform the query - they just create a “query object” with the correct parameters. To actually get the results of the query, you’ll need to execute it:

response = si.query("game").execute()

This will return a SolrResponse object. If you treat this object as a list, then each member of the list will be a document, in the form of a Python dictionary containing the relevant fields:

For example, if you run the first example query above, you should see a response like this:

>>> for result in si.query("game").execute():
...    print result

{'author_t': u'George R.R. Martin',
 'cat': (u'book',),
 'genre_s': u'fantasy',
 'id': u'0553573403',
 'inStock': True,
 'name': u'A Game of Thrones',
 'price': 7.9900000000000002,
 'sequence_i': 1,
 'series_t': u'A Song of Ice and Fire'}
{'author_t': u'Orson Scott Card',
 'cat': (u'book',),
 'genre_s': u'scifi',
 'id': u'0812550706',
 'inStock': True,
 'name': u"Ender's Game",
 'price': 6.9900000000000002,
 'sequence_i': 1,
 'series_t': u'Ender'}

Solr has returned two results. Each result is a dictionary, containing all the fields which we initially uploaded.


Multivalued fields

Because cat is declared in the schema as a multivalued field, sunburnt has returned the cat field as a tuple of results - albeit in this case both books only have one category assigned to them, so the value of the cat field is a length-one tuple.


Floating-point numbers

In both cases, although we initially provided the price to two decimal places, Solr stores the answer as a floating point number. When the result comes back, it suffers from the common problem of representing decimal numbers in binary, and the answer looks slightly unexpected.

Of course, often you don’t want your results in the form of a dictionary, you want an object. Perhaps you have the following class defined in your code:

class Book:
    def __init__(self, name, author_t, **other_kwargs):
        self.title = name
        self.author = author_t
        self.other_kwargs = other_kwargs

    def __repr__(self):
        return 'Book("%s", "%s")' % (title, author)

You can tell sunburnt to give you Book instances back by telling execute() to use the class as a constructor.

>>> for result in si.query(“game”).execute(constructor=Book):
...     print result

Book("A Game of Thrones", "George R.R. Martin")
Book("Ender's Game", "Orson Scott Card")

The constructor argument most often will be a class, but it can be any callable; it will always be called as constructor(**response_dict).

You can extract more information from the response than simply the list of results. The SolrResponse object has the following attributes:

  • response.status : status of query. (If this is not ‘0’, then something went wrong).
  • response.QTime : how long did the query take in milliseconds.
  • response.params : the params that were used in the query.

and the results themselves are in the following attributes

  • response.result : the results of your main query.
  • response.facet_counts : see Faceting below.
  • response.highlighting : see Highlighting below.
  • response.more_like_these : see More Like This below.

Finally, response.result itself has the following attributes

  • response.result.numFound : total number of docs in the index which fulfilled the query.
  • response.result.docs : the actual results themselves (more easily extracted as list(response)).
  • response.result.start : if the number of docs is less than numFound, then this is the pagination offset.

Returning different fields

By default, Solr will return all stored fields in the results. You might only be interested in a subset of those fields. To restrict the fields Solr returns, you apply the field_limit() method.

si.query("game").field_limit("id") # only return the id of each document
si.query("game").field_limit(["id", "name"]) # only return the id and name of each document

You can use the same option to get hold of the relevancy score that Solr has calculated for each document in the query:

si.query("game").field_limit(score=True) # Return the score alongside each document
si.query("game").field_limit("id", score=True") # return just the id and score.

The results appear just like the normal dictionary responses, but with a different selection of fields.

>>> for result in si.query("game").field_limit("id", score=True"):... 
    print result

{'score': 1.1931472000000001, 'id': u'0553573403'}
{'score': 1.1931472000000001, 'id': u'0812550706'}

More complex queries

Solr can index not only text fields but numbers, booleans and dates. As of version 3.1, it can also index spatial points (though sunburnt does not yet have support for spatial queries). This means you can refine your textual searches by also querying on associated numbers, booleans or dates

In our books example, there are two numerical fields - the price (which is a float) and sequence_i (which is an integer). Numerical fields can be queried:

  • exactly
  • by comparison (< / <= / >= / >)
  • by range (between two values)

Exact queries

Don’t try and query floats exactly unless you really know what you’re doing (http://download.oracle.com/docs/cd/E19957-01/806-3568/ncg_goldberg.html). Solr will let you, but you almost certainly don’t want to. Querying integers exactly is fine though.

si.query(sequence_i=1) # query for all books which are first in their sequence.

Comparison queries

These use a new syntax:

si.query(price__lt=7) # notice the double-underscore separating “price” from “lt”.

will search for all books whose price is less than 7 (dollars, I guess - the example leaves currency unspecified!). You can do similar searches on any float or integer field, and you can use:

  • gt : greater than, >
  • gte : greater than or equal to, >=
  • lt : less than, <
  • lte : less than or equal to, <=

Range queries

As an extension of a comparison query, you can query for values that are within a range, ie between two different numbers.

si.query(price__range=(5, 7)) # Search for all books with prices between $5 and $7.

This range query is inclusive - it will return prices of books which are priced at exactly $5 or exactly $7. You can also make an exclusive search:

si.query(price__rangeexc=(5, 7))

which will exclude books priced at exactly $5 or $7.

Finally, you can also do a completely open range search:


will search for a book which has any price. Why would you do this? Well, if you had a schema where price was optional, then this search would return all books which had a price - and exclude any books which didn’t have a price.

Date queries

You can query on dates the same way as you can query on numbers: exactly, by comparison, or by range. The example books data doesn’t include any date fields, so we’ll look at the example hardware data, which includes a manufacturedate_dt field.

Be warned, though, that exact searching on date suffers from similar problems to exact searching on floating point numbers. Solr stores all dates to microsecond precision; exact searching will fail unless the date requested is also correct to microsecond precision.

si.query(manufacturedate_dt=datetime.datetime(2006, 02, 13))

will search for items whose manufacture date is exactly zero microseconds after midnight on the 13th February, 2006.

More likely you’ll want to search by comparison or by range:

# all items manufactured on or after the 1st January 2006
si.query(manufacturedate_dt__gt=datetime.datetime(2006, 1, 1))

# all items manufactured in Q1 2006.
si.query(manufacturedate_dt__range=(datetime.datetime(2006, 1, 1), datetime.datetime(2006, 4, 1))

The argument to a date query can be any object that looks roughly like a Python datetime object (so mx.DateTime objects will also work), or a string in W3C Datetime notation (http://www.w3.org/TR/NOTE-datetime)

si.query(manufacturedate_dt__range=("2010-03-04 00:34:21", "2011-02-17 09:21:44"))

All of the above queries will work as you expect - bearing in mind that solr will still be working to microsecond precision. The first query above will return all results later than, or on, exactly zero microseconds after midnight, 1st January, 2006.

Boolean fields

Boolean fields are flags on a document. In the example hardware specs, documents carry an inStock field. We can select on that by doing:

si.query("Samsung", inStock=True) # all Samsung hardware which is in stock

Sorting results

Unless told otherwise, Solr will return results in “relevancy” order. How Solr determines relevancy is a complex question, and can depend highly on your specific setup. However, it’s possible to override this and sort query results by another field. This field must be sortable, so most likely you’d use a numerical or date field.

si.query("game").sort_by("price") # Sort by ascending price
si.query("game").sort_by("-price") # Sort by descending price (because of the minus sign)

You can also sort on multiple factors:


This query will sort first by descending price, and then by increasing “score” (which is what solr calls relevancy).

Excluding results from queries

In the examples above, we’ve only considered narrowing our search with positive requirements. What if we want to exclude results by some criteria? Returning to the books data again, we can exclude all Lloyd Alexander books by doing:

si.exclude(author_t="Lloyd Alexander")

exclude() methods chain in the same way as query() methodms, so you can mix and match:

si.query(price__gt=7).exclude(author_t="Lloyd Alexander")
# return all books costing more than $7, except for those authored by Lloyd Alexander.

Optional terms and combining queries

Sunburnt queries can be chained together in all sorts of ways, with query and exclude terms being applied. So far, you’ve only seen examples which have compulsory terms, either positive (query()) or negative(exclude()). What if you want to have optional terms?

The syntax for this is a little uglier. Let’s imagine we want books which either have the word “game” or the word “black” in their titles.

What we do is construct two query objects, one for each condition, and OR them together.

si.query(si.Q("game") | si.Q("black"))

The Q object can contain an arbitrary query, and can then be combined using Boolean logic (here, using |, the OR operator). The result can then be passed to a normal si.query() call for execution.

Q objects can be combined using any of the Boolean operators, so also & (AND) and ~ (NOT), and can be nested within each other. You’re unlikely to care about this unless you are constructing queries programmatically, but it’s possible to express arbitrarily complex queries in this way.

A moderately complex query could be written:

si.query(si.Q(si.Q("game") & ~si.Q(author_t="orson")) \
| si.Q(si.Q("black" & ~si.Q(author_t="lloyd")))

which will return all results which fulfil the criteria:

  • Either (books with “game” in the title which are not by authors called “orson”)
  • Or (books with “black” in the title which are not by authors called “lloyd”)

Wildcard searching

Sometimes you want to search for partial matches for a word. Depending on how your Solr schema does stemming, this may be done automatically for you. For example, in the example schema, if you search for “parse”, then documents containing “parsing” will also be returned, because Solr will reduce both the search term and the term in the document to their stem, which is “pars”.

However, sometimes you need to do partial matches that Solr doesn’t know about. You can use asterisks and question marks in the normal way, except that you may not use leading wildcards - ie no wildcards at the beginning of a term.

Using the books example again:


will search for all books which have a word beginning with “Thr” in their title. (So it will return “A Game of Thrones” and “The Book of Three”).

# will return "The Black Company", "The Book of Three" and "The Black Cauldron"

The results of a wildcard search are highly dependent on your Solr configuration, and in particular depend on what text analysis it performs. You may find you need to lowercase your search term even if the original document was mixed cased, because Solr has lowercased the document before indexing it. (We have done this here).

If, for some reason, you want to search exactly for a string with an asterisk or a question mark in it then you need to tell Solr to special case it:


This will search for a document whose id contains exactly the string given, including the question mark and asterisk. (Since there isn’t one in our index, that will return no results.)

Filter queries and caching

Solr implements several internal caching layers, and to some extent you can control when and how they’re used. (This is separate from the HTTP caching layer).

Often, you find that you can partition your query; one part is run many times without change, or with very limited change, and another part varies much more. (See http://wiki.apache.org/solr/FilterQueryGuidance for more guidance.)

You can get Solr to cache the infrequently-varying part of the query by use of the FilterCache. For example, in the books case, you might provide standard functionality to filter results by various price ranges: less than $7.50, or greater than $7.50. This portion of your search will be run identically for nearly every query, while the main textual part of the query varies lots.

If you separate out these two parts to the query, you can mark the price query as being cacheable, by doing a filter query instead of a normal query for that part of the search.

If you taking search input from the user, you would write:


The filter() method has the same functionality as the query() method, in terms of datatypes and query types. However, it also tells Solr to separate out that part of the query and cache the results. In this case, Solr will precompute the price portion of the query and cache the results, so that as the user-driven queries vary, Solr only has to perform in full the unique portion of the query, the name query, and the price filter can be applied much more rapidly.

You can filter any sort of query, simply by using filter() instead of query(). And if your filtering involves an exclusion, then filter_exclude() has the same functionality as exclude().

# Might be useful if a substantial portion of your users hate authors called “Lloyd”.

If it’s useful, you can mix and match query() and filter() calls as much as you like while chaining. The resulting filter queries will be combined and cached together.


and the argument to a filter() or filter_exclude() call can be a Boolean combination of si.Q objects.

Query boosting

Solr provides a mechanism for “boosting” results according to the values of various fields (See http://wiki.apache.org/solr/SolrRelevancyCookbook#Boosting_Ranking_Terms for a full explanation). This is only useful where you’re doing a search with optional terms, and you want to specify that some of these terms are more important than others.

For example, imagine you are searching for books which either have “black” in the title, or have an author named “lloyd”. Let’s say that although either will do, you care more about the author than the title. You can express this in sunburnt by raising a Q object to a power equivalent to the boost you want.

si.query(si.Q("black") | si.Q(author_t="lloyd")**3)

This boosts the importance of the author field by 3. The number is a fairly arbitrary parameter, and it’s something of a black art to choose the relevant value.

A more common pattern is that you want all books with “black” in the title and you have a preference for those authored by Lloyd Alexander. This is different from the last query; the last query would return books by Lloyd Alexander which did not have “black” in the title. Achieving this in solr is possible, but a little awkward; sunburnt provides a shortcut for this pattern.

si.query("black").boost_relevancy(3, author_t="lloyd")

This is fully chainable, and boost_relevancy can take an arbitrary collection of query objects.


For background, see http://wiki.apache.org/solr/SimpleFacetParameters.

Sunburnt lets you apply faceting to any query, with the facet_by() method, chainable on a query object. The facet_by() method needs, at least, a field (or list of fields) to facet on:

facet_query = si.query("game").facet_by("sequence_i").paginate(rows=0)

The above fragment will search for game with “thrones” in the title, and facet the results according to the value of sequence_i. It will also return zero results, just the facet output.

>>> print facet_query.execute().facet_counts.facet_fields

{'sequence_i': [('1', 2), ('2', 0), ('3', 0)]}

The facet_counts objects contains several sets of results - here, we’re only interested in the facet_fields object. This contains a dictionary of results, keyed by each field where faceting was requested. (In this case, we only requested faceting on one field). The dictionary value is a list of two-tuples, mapping the value of the faceted field (in this case, sequence_i takes the values ‘1’, ‘2’, or ‘3’) to the numbers of results for each value.

You can read the above result as saying: ‘of all the books which have “game” in their title, 2 of them have sequence_i=1, 0 of them have sequence_i=2, and 0 of them have sequence_i=3‘.

You can facet on more than one field at a time:

si.query(...).facet_by(fields=["field1", "field2, ...])

and the facet_fields dictionary will have more than one key.

Solr supports a number of parameters to the faceting operation. All of the basic options are exposed through sunburnt:

fields, prefix, sort, limit, offset, mincount, missing, method, enum.cache.minDf

All of these can be used as keyword arguments to the facet() call, except of course the last one since it contains periods. To pass keyword arguments with periods in them, you can use ** syntax:


You can also facet on the result of one or more queries, using the facet_query() method. For example:

>>> fquery = si.query("game").facet_query(price__lt=7).facet_query(price__gte=7)
>>> print fquery.execute().facet_counts.facet_queries

[('price:[7.0 TO *]', 1), ('price:{* TO 7.0}', 1)]

This will facet the results according to the two queries specified, so you can see how many of the results cost less than $7, and how many cost more.

The results come back this time in the facet_queries object, but have the same form as before. The facets are shown as a list of tuples, mapping query to number of results. You can read the above as saying ‘of the results, 1 of them fulfilled the first facet-query (price greater than 7) and 1 of them fulfilled the second query-facet (price less than 7)‘.


Other types of facet

Currently, faceting by date and range are not currently supported (but some of their functionality can be replicated by using facet_query()). Nor are LocalParams or pivot faceting.


For background, see http://wiki.apache.org/solr/HighlightingParameters.

Alongside the normal search results, you can ask solr to return fragments of the documents, with relevant search terms highlighted. You do this with the chainable highlight() method. By default this will highlight values in the default search field. In our books example, the default search field is a generated field, not returned in the results, so we’ll need to explicitly specify which field we would like to see highlighted:

>>> highlight_query = si.query("game").highlight("name")
>>> print highlight_query.execute().highlighting

{'0553573403': {'name': ['A <em>Game</em> of Thrones']},
 '0812550706': {'name': ["Ender's <em>Game</em>"]}}

The highlighting results live in the highlighting attribute on the SolrResponse object. The results are shown as a dictionary of dictionaries. The top-level key is the ID (or uniqueKey) of each document returned. For each document, you then have a dictionary mapping field names to fragments of highlighted text. In this case we only asked for highlighting on the name field. Multiple fragments might be returned for each field, though in this case we only get one fragment each. The text is highlighted with HTML, and the fragments should be suitable for dropping straight into a search template.

If you are using the default result format (that is, if you are not specifying a constructor option when you call execute()), highlighting results for a single result can be accessed on the individual result item as a dictionary in a solr_highlights field. For example, with the highlighted query above, you could access highlight snippets for the name field on an individual result as result['solr_highlights']['name']. This is particularly convenient for displaying highlighted text snippets in a template; e.g., displaying highlights in a Django template might look like this:

{% for snippet in book.solr_highlights.name %}
   <p>... {{ snippet|safe }} ...</p>
{% endfor %}


The solr_highlights field will only be available on a result item if highlights were found for that record.

Again, Solr supports a large number of options to the highlighting command, and all of these are exposed through sunburnt. The full list of supported options is:

fields, snippets, fragsize, mergeContinuous, requireFieldMatch, maxAnalyzedChars,
alternateField, maxAlternateFieldLength, formatter, simple.pre.simple.post,
fragmenter, usePhrasehighlighter, hilightMultiTerm, regex.slop, regex.pattern,

See the note above in Faceting about using keyword arguments with periods.

More Like This

For background, see http://wiki.apache.org/solr/MoreLikeThis. Alongside a set of search results, Solr can suggest other documents that are similar to each of the documents in the search result.


Query handlers

Sunburnt only supports MoreLikeThis through the StandardQueryHandler, not through the separate MoreLikeThisHandler. That is, it only supports more-like-this searches on documents that are already in its index.

More-like-this searches are accomplished with the mlt() chainable option. Solr needs to know which fields to consider when deciding similarity; if you don’t make any choice, then the default field (specified by schema.xml) will be used.

>>> mlt_query = si.query(id="0553573403").mlt("name", mintd=1, mindf=1)
>>> mlt_results = mlt_query.execute().more_like_these
>>> print mlt_results

{'0553573403': <sunburnt.schema.SolrResult object at 0x4b10510>}

>>> print mlt_results['0553573403'].docs

[{'author_t': u'Orson Scott Card',
  'cat': (u'book',),
  'genre_s': u'scifi',
  'id': u'0812550706',
  'inStock': True,
  'name': u"Ender's Game",
  'price': 6.9900000000000002,
  'sequence_i': 1,
  'series_t': u'Ender'}]

Here we used mlt() options to alter the default behaviour (because our corpus is so small that Solr wouldn’t find any similar documents with the standard behaviour.

The SolrResponse object has a more_like_these attribute. This is a dictionary of SolrResult objects, one dictionary entry for each result of the main query. Here, the query only produced one result (because we searched on the uniqueKey. Inspecting the SolrResult object, we find that it contains only one document.

We can read the above result as saying that under the mlt() parameters requested, there was only one document similar to the search result.

In this case, only one document was returned by the original query, In this case, there is a shortcut attribute: more_like_this instead of more_like_these.

>>> print mlt_query.execute().more_like_this.docs

[{'author_t': u'Orson Scott Card',

to avoid having to do the extra dictionary lookup.

mlt() also takes a list of options (see the Solr documentation for a full explanation);

fields, count, mintf, mindf, minwl, mawl, maxqt, maxntp, boost

Spatial fields

From version 3.1 of Solr, spatial field-types are supported in the schema. This means you can have fields on a document representing (latitude, longitude) pairs. (Indeed, you can have fields representing points in an arbitrary number of dimensions.)

Although sunburnt deals correctly storage and retrieval of such fields, currently no querying is supported beyond exact matching (including spatial querying).

sunburnt expects spatial fields to be supplied as iterables of length two, and will always return them as two-tuples.

Binary fields

From version 3.1 of Solr, fields for binary data are supported in the schema. In Solr these are stored as base64-encoded blobs, but as a sunburnt user you don’t have to care about this. Sunburnt will automatically transcode to and from base64 as appropriate, and your results will contain a binary string where appropriate. (Querying on Binary Fields is not supported, and doesn’t make much sense anyway).

UUID fields

From version 1.4 of Solr, fields for UUIDs are supported in the schema (see http://wiki.apache.org/solr/UniqueKey). When retrieving results, Solr will automatically translate any UUID fields into python UUID objects (see http://docs.python.org/library/uuid.html). When inserting documents, sunburnt will accept values which are either UUID objects or UUID strings; or the string “NEW”, to indicate that a UUID should be created on ingestion.